The Process and Instrumentation Diagram is an extension from early developmental block diagrams and process flow diagrams. It defines the process in a schematic format providing documentation of how the process works. These documents also provide equipment counts (valves, tanks, pumps and device numbers for programming).

The P&ID is a fundamental communication tool for process design and automation.  In early process development it is an extension block diagrams and process flow diagrams. The P&ID is a form of schematic that shows all aspects of the system including all the equipment and instrumentation.   It provides a clear picture of the process and with design parametetrates, temperatures, pre, equipment, design rates,